Field of the Invention
The present invention relates to a fixing apparatus provided in an image forming apparatus using electrophotography.
Description of the Related Art
An image forming apparatus, such as a laser beam printer or an LED printer, includes a fixing apparatus that heat-fixes an unfixed toner image formed on a recording material onto the recording material. A fixing apparatus using a low-heat-capacity cylindrical film is known. Such a fixing apparatus generally includes a film, a heater in contact with an inner surface of the film, and a pressurizing roller that forms a nip portion with the heater with the film being disposed there between. The warm-up time of the fixing apparatus is short, and this can contribute to shortening of First Print Output Time (FPOT) of the image forming apparatus.
In this fixing apparatus, the film generally rotates due to rotation of the pressurizing roller. However, when a recording material absorbing moisture is conveyed and heated in the nip portion, vapor is sometimes produced near the nip portion. In particular, vapor is likely to be emitted to a surface of the pressurizing roller opposed to a surface of the recording material where a toner image is not formed. Condensation is caused, by the vapor, on the surface of the pressurizing roller. As a result, a phenomenon called “condensation slippage” occurs in which the frictional force of the pressurizing roller with the recording material and the film decreases and conveyance of the recording material becomes unstable.
Accordingly, Japanese Patent Laid-Open No. 2007-206275 discloses a structure in which a duct is provided such that an image forming apparatus and the inside of a fixing apparatus are connected there through and vapor near a pressurizing roller is scattered by blowing outside air against the pressurizing roller through the duct to realize stable conveyance of a recording material.
However, in the structure disclosed in Japanese Patent Laid-Open No. 2007-206275 in which air taken in from the outside of the fixing apparatus is directly sent to the pressurizing roller, the temperature of the pressurizing roller sometimes excessively decreases. Although it is conceivable to discharge air from the inside of the fixing apparatus to the outside, this is difficult under layout restrictions because it is necessary to discharge air from a portion near the nip portion where vapor is produced.